hey what exactly would you like to achieve with the redirect?
would you like to redirect any attachment page to your frontpage?
yoast works with lay theme. it just doesnt recognize the text in the gridder so it says there is no text on the page.
but google finds that text and other than that creating meta tags with yoast works as far as i know.
why are attachment pages bad for seo?
afaik seo is just about the kind of text you have on your page and alt tags and meta tags. all of this you can do with lay theme, just individual meta tags for individual pages is not supported.